Changing the orientation of the head with regard to gravity causes a dramatic change in ocular compensatory movements generated by the vestibular system. Rotation about axes titled from the vertical causes continuous nystagmus for as long as the stimulus persists and cancels the post-rotatory response when the rotation stops. A similar effect is produced by pitching the head to and fro while rotating about a vertical axis (Raphan et al., 1981). The aim of this research is to characterize the dynamics of the slow phase velocity of nystagmus induced by pitching during rotation and to compare it to that induced by rotation about an off-vertical axis. Specifically we will determine the gain of the response, the saturation velocity, and the interaction with the post-rotatory response when the animal is stopped. This should enable us to elucidate the nature of the coupling from the labyrinth to the velocity storage mechanism or integrator that appears to be a focus for generating nystagmus from the vestibular as well as the visual system. Extracellular unit activity will be recorded in the vestibular nerve and the vestibular nuclei. Slow phase eye velocity and unit activity will be analyzed in the time and frequency domains using computer programs which have been devised recently. Eye movement and unit data will be compared to determine if changes in eye velocity accuragely reflect changes in unit activity. This relationship will be compared to that kpredicted by our model of the organization of the system generating slow phase velocity of vestibular and optoinetic nystagmus. A particularly interesting feature of this stimulus is that it engages all parts of the labyrinth, and according to our predictions, a contribution from each part is necessary to generate accurate compensatory eye velocities. This research should give greater insight into how the vertical and horizontal semicircular canals as well as the otoliths couple to the vestibular nuclei and oculomotor nuclei through the velocity storage mechanism to generate nystagmus.